In conventional manner, that type of shutter is situated, at least in part, inside the duct connecting the dispenser member to the connection sleeve. In addition, the shutter is often resiliently biased by spring means towards the dispenser orifice. Under such circumstances, it should be understood that the shutter is an internal shutter situated inside the dispenser head, and that the dispenser orifice is opened by retracting the shutter further into the dispenser head.
Document FR-2 654 079 describes a dispenser head incorporating such a shutter. In that document, the shutter is housed inside the dispenser head below the press surface on which it is possible to press in order to actuate the dispenser member. At one of its ends, the shutter includes a plunger pin designed to come selectively into leaktight contact with the dispenser orifice. At its opposite end, the shutter defines spring means in the form of an elastically deformable strip which bears against the body of the dispenser head. Furthermore, shutter displacement means are provided in the form of a cam secured to the bearing surface. Under such circumstances, the bearing surface is elastically deformable so that it is possible to press down the cam through the shutter, which thus forms an actuator window. By lowering the cam in this way, by pressing down on the press surface, the shutter is moved towards the inside of the dispenser head by deforming its resilient strip. This movement withdraws the plunger pin from the dispenser orifice, and thus releases an outlet passage for the fluid under pressure.
In the dispenser head in that French document, the shutter is moved to release the dispenser orifice by means of a cam, as described above. However, other means for moving the shutter can be envisaged. For example, the shutter can form a piston slidably housed inside a chamber. Thus, when the fluid under pressure arrives in the chamber, the piston is pushed back to slide against spring means, thereby withdrawing the plunger pin from the dispenser orifice. Consequently, it can be seen that various means for moving the shutter are possible. In any event, the present invention relates more particularly to shutters having a plunger pin that is resiliently biased by spring means.
In dispenser heads having shutters that are resiliently biased, it is very difficult to control the force with which the spring means press the plunger pin into the dispenser orifice. Naturally, the force is proportional to the intrinsic stiffness of the spring means, but it is also proportional to their position inside the dispenser head. Furthermore, friction forces have an influence on the pressure force. A major drawback with that type of shutter resides in the fact that, sometimes, the plunger pin is pressed too far into the dispenser orifice so that it remains jammed therein. It is then no longer possible to use the dispenser head, and consequently the dispenser member (the pump or the valve). Furthermore, even when the plunger pin does not remain literally jammed in the dispenser orifice, the shutter may remain temporarily jammed, and that it bursts free suddenly when the press surface of the dispenser head is pressed down hard. Thus, as a result, and contrary to the desired effect, the fluid is dispensed in a violent or explosive manner. Naturally, all of these drawbacks are associated with the lack of mastery or of control over the thrust force exerted by the spring means on the dispenser orifice.